Vehicle Exhaust Treatment Systems

ABSTRACT

A vehicle engine exhaust gas treatment system ( 10 ) for use on a tractor comprising storage means ( 11 ) for storing urea, injector means ( 13 ) for injecting urea into a catalytic converter ( 21 ) located in an exhaust ( 22 ) of an engine ( 23 ), an air duct ( 29;30 ) via which air is drawn into the engine, and cooling means for cooling the urea on its passage from the storage means to the injector means, the cooling means comprising a heat exchanger which includes an inner pipe ( 15; 17 ) through which the urea flows on its way to the injector means, the inner pipe extending within the air duct ( 29;30 ) to cool the urea.

The invention relates to treatment systems for treating exhaust gasesfrom an internal combustion engine of a vehicle, particularly, but notexclusively so, a tractor.

It is well known to provide a vehicle exhaust gas treatment system inwhich a urea solution is injected into a catalytic converter located inthe exhaust system of an internal combustion engine, to significantlyreduce the level of exhaust pollutants such as carbon monoxide, nitrogenoxide and particulate matter in the exhaust gases.

Problems arise with such treatment systems since if the temperature ofthe urea exceeds 60° C., due to exposure to the sun or the closeproximity of hot components on the vehicle, the urea starts to breakdown into corrosive constituents which can damage the components of thetreatment system.

It is an object of the present invention to provide an improvedtreatment system which at least mitigates the above problem.

Thus according to the present invention there is provided a vehicleengine exhaust gas treatment system for use on a tractor comprisingstorage means for storing urea, injector means for injecting urea into acatalytic converter located in an exhaust of an engine, an air duct viawhich air is drawn into the engine, and cooling means for cooling theurea on its passage from the storage means to the injector means, thecooling means comprising a heat exchanger which includes an inner pipethrough which the urea flows on its way to the injector means, the innerpipe extending within the air duct to cool the urea.

Conveniently, on a vehicle such as an agricultural or industrial tractorwhich is provided with an engine turbo-charger, the inner pipe isexposed to the air which is drawn into the turbo-charger. Typically suchair which is drawn in from around the tractor has a maximum temperatureof 45° C. and a high mass flow rate of 10-25 cubic metres per minute.Thus this air flow is not heated up significantly on its passage to theturbo-charger. The invention can also be used on non turbo-chargedengines.

Normally, air is drawn into the engine via an air filter and, inaccordance with the present invention, the inner pipe of the heatexchanger may be located on one or both sides of the air filter toincrease the cooling effect on the urea.

If the tractor is provided with an air compressor the urea may beadditionally or alternatively cooled by exposing the heat exchanger tothe flow of air which is being drawn into the compressor. Typically suchair which is drawn into an air compressor reaches a maximum temperatureof 45° C. which is the ambient air temperature as explained above.

In a vehicle having a fuel tank for the supply of fuel to an engine ofthe vehicle and a urea tank for the supply of urea for injection intothe engine exhaust system, the urea tank may be located relative to thefuel tank so that the fuel in the fuel tank at least partially insulatesthe urea from the heating effect of the sun and other heat sources (forexample the heating effects of the exhaust of the engine and the coolingsystem of the engine).

In a preferred construction the urea tank is completely surrounded bythe fuel in the fuel tank to obtain the maximum insulating effect fromthe fuel. Preferably further still, the fuel tank is formed of mouldedplastic wherein a wall of the fuel tank comprises a concavity whichdefines the volume of the urea storage tank, and wherein a closureelement covers the concavity.

In accordance with the further aspect of the present invention, there isprovided a multi compartment vessel for fixing to a vehicle, the vesselincluding a fuel tank formed of moulded plastic, wherein a wall of thefuel tank comprises a concavity which defines the volume of a ureastorage tank for storing urea, the vessel further comprising a closureelement over the concavity.

Advantageously, by forming the fuel tank of moulded plastic with aconcavity in this way, the manufacturing and assembly process issimplified.

The present invention will now be described, by way of example only,with reference to the accompanying drawings in which:

FIG. 1 shows diagrammatically a vehicle exhaust gas treatment system inaccordance with the present invention;

FIGS. 2 & 3 show perspective and part-sectional views through a combinedfuel and urea tank in accordance with a second aspect of the presentinvention;

FIG. 4 shows an enlarged view of part Y shown in FIG. 3; and,

FIG. 5 shows details of a heat exchanger associated with a compressorair supply duct.

Referring to the drawings, an engine exhaust gas treatment system 10 hasa urea solution supply tank 11 which supplies a urea supply module 12which in turn supplies a urea injector 13 via line sections 14 to 20.Injector 13 injects the urea into a Selective Catalytic Reduction (SCR)catalytic converter 21 which is located in the exhaust system 22 of theengine 23. The engine has a turbo-charger 24 which has an input section24 a through which the air drawn through air filter 25 enters the enginevia an air cooler 26. The exhaust gases leaving the engine 23 passthrough the exit stage 24 b of the turbo-charger in a conventionalmanner and then flow past the injector 13 and through the catalyticconverter 21 on their way to the exit of the exhaust system 22.

The vehicle is also provided with an air compressor 27 to power variouspneumatic functions on the vehicle such as air brakes and an airsuspension system for the cab. This air compressor is fed with air via aduct 28 which receives air via the air filter 25.

The air which is drawn into the turbo-charger intake stage 24 a passesthrough duct 29 before passing through air filter 25 and the furtherduct 30 after passing through the air filter.

In accordance with the present invention, the urea passes from thesupply module 12 to the injector 13 via fine sections 15, 17 and 19 atwhich locations the urea flowing through the sections 15, 17, and 19 isexposed to the air flowing through air ducts 29, 30 and 28 respectively.

FIG. 5 shows details of a heat exchanger arrangement which can be usedin connection with the air duct 28 which supplies air to the compressor27. In this arrangement a heat exchange core is provided by a pipe 31which forms the section 19 of the supply line and which exposes the ureato the cooling effect of the air which is being drawn into the aircompressor 27 via the duct 28.

Similarly in sections 15 and 17 of the supply line a pipe through whichthe urea flows can be arranged to extend within air ducts 29 and 30 inorder to be exposed to the air flowing through air ducts 29 and 30respectively.

As will be appreciated since the air which is drawn into the enginenormally has a maximum temperature of 45° C. this should maintain thetemperature of the urea well below the critical 60° C. temperature atwhich decomposition occurs.

Although in the arrangement described above the urea is cooled in ducts29, 30 and 28 it may, for example, only be cooled in duct 29 or 30, i.e.before or after passage through the air filter 25 and in machines whichare not provided with an air compressor the further cooling in duct 28will not occur. Conversely, if the cooling effect is adequate, the ureamay only be cooled using the air which is to be drawn into thecompressor via duct 28.

The urea in tank 11 is further shielded from the effects of the sun andother influences by locating the urea tank 11 such that the fuel in thefuel tank 32 of the vehicle at the least partially insulates the ureafrom the heating effects of the sun and the heating effects of theexhaust of the engine. This tank arrangement also provides insulationfrom the heat coming from the cooling system of the engine as thecooling air may be directed downwardly after passing through the enginebay to an area where the fuel tank or tanks are often positioned.

In a preferred arrangement shown in FIGS. 2 & 3, the urea tank 11 iscompletely surrounded by the fuel tank 32 to provide maximum heatinsulation. In certain tank configurations the urea tank may not besurrounded by the fuel tank but simply immediately adjacent thereto(with the urea tank being divided from the fuel tank by a common wallfor example) so that the urea tank is shielded from the direct heatingeffects of the sun and the heating effects of the exhaust of the engineand the cooling air of the engine as discussed above.

In FIGS. 2, 3 and 4, the fuel tank 32 has a fuel filler spout 33 and theurea tank 11 has a urea filler spout 34. Fuel is drawn out of tank 32via pipe 35 using a conventional electric fuel pump (not shown) and afuel gauge 36 is also provided. A feed tube 37 is provided for thesupply of urea to the module 12 from tank 11 via line 12 a. The returnof any surplus urea from the supply module 12 to the tank 11 is via line12 b.

The fuel tank 32 is formed from a single plastic structure manufacturedby a rotational moulding process. Such processes are known and will notbe described in detail. However, reference is invited to web pagehttp://en.wikipedia.org/wiki/Rotational molding for further details.

With reference to FIGS. 3 and 4, the fuel tank 32 is defined by a closedvolume 32 a having an outside surface 32 b, a bottom surface 32 c and atop surface 32 d. Within the top surface 32 d a concavity 11 a isprovided (also by the moulding process) which defines the volume for theurea tank 11. The concavity 11 a includes near vertical walls 11 b and abase 11 c.

The concavity 11 a is closed by a cover 50 which is secured to the topsurface 32 b of the fuel tank 32 by ultrasonic welding (FIG. 4).Therefore, the cover 50 is sealed around its edge to prevent leakage.The fuel gauge 36 and feed tube 37 are inserted and secured in the cover50.

Alternatively, the cover 50 may be screwed to the tank 32. In this case,metal inserts may be provided in the tank 32 to receive the screws.

From reading the present disclosure, other modification will be apparentto persons skilled in the art. Such modifications may involve otherfeatures which are already known in the field of vehicle exhausttreatment systems and component parts therefore and which may be usedinstead of or in addition to features already described herein.

1. A vehicle engine exhaust gas treatment system for use on a tractorcomprising storage means for storing urea, injector means for injectingurea into a catalytic converter located in an exhaust of an engine, anair duct via which air is drawn into the engine, and cooling means forcooling the urea on its passage from the storage means to the injectormeans, the cooling means comprising a heat exchanger which includes aninner pipe through which the urea flows on its way to the injectormeans, the inner pipe extending within the air duct to cool the urea. 2.A system according to claim 1 in which the air is drawn into the enginevia an air filter and the inner pipe extends within the air duct on oneor both sides of the air filter to increase the cooling effect on theurea.
 3. A system according to claim 1, in which the vehicle has an aircompressor, the urea being additionally or alternatively cooled byexposing the inner pipe to the flow of air which is being drawn into thecompressor.
 4. A system according to claim 1 in which the vehicle has afuel tank for the supply of fuel to an engine of the vehicle and theurea storage means comprises a urea tank located relative to the fueltank so that the fuel in the fuel tank at least partially insulates theurea from the heating effect of the sun and other heat sources. 5.(canceled)
 6. A system according to claim 4, in which the urea tank canbe completely surrounded by fuel in the fuel tank to obtain the maximuminsulating effect from the fuel.
 7. A system according to claim 6,wherein the fuel tank is formed of moulded plastic wherein a wall of thefuel tank comprises a concavity which defines the volume of the ureastorage tank, and wherein a closure element covers the concavity.
 8. Asystem according to claim 7, wherein the fuel tank is formed by arotational moulding process.
 9. A multi compartment vessel for fixing toa vehicle, the vessel including a fuel tank formed of moulded plastic,wherein a wall of the fuel tank comprises a concavity which defines thevolume of a urea storage tank for storing urea, the vessel furthercomprising a closure element over the concavity.